Accelerated separation of GC-amenable lipid classes in plant oils by countercurrent chromatography in the co-current mode

Abstract

Triacylglycerols represent the major part (>90%) in most plant oils and have to be eliminated, when the minor compounds such as phytosterols or tocopherols should be analyzed. Here, we used an all liquid-liquid chromatographic technique, countercurrent chromatography (CCC), to fractionate the minor lipids before gas chromatography (GC) analysis. To cover the wide range of polarity of the minor compounds, we used the co-current mode, in which both mobile and stationary phase are pumped through the system. This allowed to elute substances which partitioned almost exclusively in the stationary phase within 90 min. After testing with standard compounds, the method was applied to the separation of sesame oil and sunflower oil samples. The abundant triacylglycerols could be effectively separated from tocopherols, phytosterols, diacylglycerols, and free fatty acids in the samples, and these compounds could be analyzed (after trimethylsilylation) by GC coupled with mass spectrometry. After the enrichment caused by the CCC fractionation, we were also able to identify the tocopherol derivative α-tocomonoenol, which had not been described in sunflower oil before. Also, separation of sesame oil yielded a mixture of the polar compounds sesamin and sesamolin without further impurities.

Countercurrent chromatographic isolation and purification of 11′-α-tocomonoenol from the vitamin E extract of palm oil

“…This finding was verified by the estimation of the concentration of -T1 in palm oil with the help of the response factor of -tocopherol because the target compound was not available as standard [8,10]. Subsequently, -T1 was also qualitatively detected in roasted pumpkin seed oil from Slovenia and in sunflower oil [11,12].…”

“…capillary column coated with 0.1 μm film thickness dimethylpolysiloxane (Rtx-1; Restek, Bellefonte, PA, USA), which was previously described in detail [12]. Only the GC oven program was slightly different: It started for 1 min at 60 °C, followed by a ramp of 10 °C/min until the final temperature 320 °C, which was held for 14 min (total run time: 39 min).…”

“…Only the GC oven program was slightly different: It started for 1 min at 60 °C, followed by a ramp of 10 °C/min until the final temperature 320 °C, which was held for 14 min (total run time: 39 min). All samples were silylated prior to GC/MS analysis as recently described in detail [12].…”

Heart‐Cut Two‐Dimensional Countercurrent Chromatography for the Isolation of a Furan Fatty Acid Triacylglycerol from Latex Gloves and Identification of Further Lipid Compounds

“…From these solutions, aliquots were taken (corresponding with 50–100 μg lipids) and subjected to trimethylsilylation in a second amber 1.5 mL vial (Table S2). These aliquots of the CCC fractions were evaporated to dryness at 40 °C using a gentle stream of nitrogen and trimethylsilylated with 50 μL BSTFA/TMCS (99:1, v/v ) and 25 μL distilled pyridine according to Hammann et al (, ). Trimethylsilylated analytes were then redissolved in 1 mL of a solution with 5α‐cholestane (3.14 μg/mL, internal standard) in n ‐hexane and measured by GC/MS system I.…”

“…Samples of CCC fractions were measured with system I which consisted of a 6890 Series Plus/5973 GC/MS system equipped with a cool on‐column inlet (Hewlett‐Packard/Agilent, Waldbronn, Germany) and a precolumn (2 m × 0.53 mm i.d., deactivated with 1,3‐diphenyl‐1,1,3,3‐tetramethyldisilazane; BGB Analytics, Böckten, Switzerland) (Hammann et al, , ). The precolumn was connected to a 15 m × 0.32 mm i.d., capillary column coated with 0.1‐μm film thickness dimethyl polysiloxane (DB‐1, Agilent J&W, Waldbronn, Germany).…”